Alice Walker at her home in Berkeley, California Photograph: Noah Berger/Associated Press

On the way to the Riverside Church in New York to hear Alice Walker reading from her new collection of essays, We Are the Ones We Have Been Waiting For, I wonder which Walker I will find poised at the podium. Will it be the glamorous feminist icon who inspired me when I was growing up as a beleaguered Pakistani in Britain in the 1980s? The strong black woman who survived a tough, working-class upbringing in the white supremacist south; defied the Klan by marrying a Jewish man, Mel Levanthal, in segregated Mississippi (when such interracial marriages were still illegal); and went on to win the Pulitzer prize for her novel The Color Purple in 1983?

Or will it be the one from the cover photo of her new book - all new age beneficence and wooden beads? The woman whose later work has been accused of an airy self-indulgence and a distinctively Californian vapidity? (In 2004, her last novel, Now is the Time to Open Your Heart, provoked the now infamous review from the New York Times's critic, Michiko Kakutani, "If this novel did not boast the name of Alice Walker, who won acclaim some two decades ago with The Color Purple, it's hard to imagine how it could have been published ... [it is] a remarkably awful compendium of inanities.") On the large stage in the cavernous church she looks small and monkish, "a woman holy and alone" as one reviewer described her in 1979. Reading steadily in her calming southern accent, she intones about the metaphysical pause, an idea drawn from the I Ching, and says that Congress should have "paused" after September 11 rather than acted in haste. The crowd looks confused - some old folk even doze off. By and large, they don't seem to mind though; this devoted congregation are here to worship their high priestess of the left and the left-behind, who, in turn, seems serenely unaware of the growing vibe of collective bafflement.

Walker's more esoteric meanderings might remain a blur, but her top-line message - that right-thinking Americans need to stand up and be counted - chimes deeply a few weeks after the Democrat victories in the US mid-term elections. As Walker writes of an anti- Iraq protest at which she was arrested just before the war started: "I had been arrested before. Those were serious times, but this time felt different. This time felt like: All the information is in."

Face to face over tea at a boutique hotel in New York's SoHo the next day, I meet a completely different Walker - a combination of natural authority, deep warmth and a flinty intelligence. She is, as Americans say, "very present" throughout the interview. At 62, she is also shockingly sexy, and looks 35. She is pumped up from a fiery exchange on live radio about her friend, Fidel Castro.

Walker's new collection marks her move to the ultra-political, not-for-profit New Press - because her regular publisher, Random House, didn't want to print it. Although Wendy Weil, her agent of 35 years, plays down the move (saying Random House still "retains an option") this is surely significant?

"Sucking up to the biggies won't get us anywhere," says Walker.

In places, this new collection of righteous speeches and essays, just published in the US, is Walker the cultural pioneer back on top form. It's packed with rousing, state of the nation stuff like this: "Hurricane Katrina may well be the start of a massive unravelling of everything we thought whole. And like the former Soviet Union we may find all our hopes for a system we have believed in dashed. What will be left?" She calls for a moratorium on childbirth for the sake of the environment ('not one more child should be born on this planet until certain conditions are met ... the most important of these is that several missing pounds of plutonium are found") and celebrates oral sex.But there are also sections that seem to derive from the far, far, left-field. The reference to her pet dog's star sign and the "how-to" guide to wearing symbolic threads on your wrist in honour of the Earth can be both infuriating and distracting.

I wonder whether she ever feels ignored these days? "I don't really notice," she says, "because at the same time as I may have been relegated to wherever they relegate people, The Color Purple is a smash on Broadway and my books sell really, really well. So I in no way feel relegated, I feel fine." The southern accent deepens slightly when she says anything earthy or defiant.

"I'm like a fig tree and I'm just putting out the figs and then there is a job that the people who get it have. It's their job to translate it into the language their mothers, their sisters, their cousins can understand. That happened with The Color Purple." It has sold 5m copies in 25 languages and has been made into a musical produced by Oprah Winfrey.

The cultural imperialism and parochialism of American culture is a recurring theme throughout the new collection, as is the optimistic reminder that, "What is foreign can be known." I ask what she makes of the controversy that has been rumbling in the UK regarding the wearing of the niqab. She immediately plugs into the political nuances. "In Possessing the Secret of Joy, there is an African woman who comes from a society where female genital mutilation is practised, and, because her home has been destroyed, her people have been dispersed, she feels like she's lost her connection to who she is. She decides she has to be genitally cut. Women have to be extremely careful about choosing something that they consider an act of defiance that can really be used to further their enslavement.

"I'm not convinced that women have the education or the sense of their own history enough or that they understand the cruelty of which men are capable and the delight that many men will take in seeing you choose to chain yourself - then they get to say 'See, you did it yourself'. Like we wear these high heels that hurt us, well it's foot-binding, you know, but we think by now, 'that's very sexy' ... "It's very, very dangerous, that's all I would say. I'm for women choosing whatever they want to do but they have to really know what they are doing. If I had to offer any counsel I would say [to British Muslim women] 'Use some of this time not just to be on the defensive but to interrogate your own culture and see how much of it you really believe yourself in your heart and how much of it you can let go of. You don't have to be a prisoner of your religion.'"

I tell her people are still fascinated by her love affair with the singer Tracy Chapman in the mid-1990s. Moments earlier she had said firmly but politely that she didn't want to answer any questions about her family life. (Her daughter Rebecca, from her marriage to Levanthal, published a frank memoir in 2000 in which she criticised the self-absorption of both parents after their divorce.) So I was surprised to see her face light up at the mention of Chapman. "Yeah I loved it too. Absolutely."

Why was it kept so quiet at the time? "It was quiet to you maybe but that's because you didn't live in our area," she answers with a throaty laugh. She has written about the relationship in her journals, which she plans to publish one day. So why did they decide against using their relationship to make a big social impact like other celebrity lesbian couples, such as Ellen DeGeneres and Anne Heche, have in the past? The idea seems to amuse her. "I would never do that. My life is not to be somebody else's impact - you know what I mean? And it was delicious and lovely and wonderful and I totally enjoyed it and I was completely in love with her but it was not anybody's business but ours."

Walker has no intention of retiring but tells me that, "In the tradition of the world when people reach their 60s, they withdraw. They become sages ... In South Korea they believe that when you turn 60, you've become a baby again and the rest of your life should be totally about joy and happiness and people should leave you alone and I just think that that's the height of intelligence. It's about strategically understanding that you need to retreat."

Walker doesn't seem to be retreating to me, though. The world has caught up with many of the big ideas that she championed in her early work, and so she naturally seems progressive these days, rather than as revolutionary and defiant as she once did. And, despite all the criticisms of her work, she still seems very relevant. Any feminist who can connect up female genital mutilation, the niqab and high heels gets my vote.